The ending number will increase to "-100", then it will be "-100-2". This is to avoid ruining intentional numbers such as "It's over 9000" or "A day in 2013". It's unlikely enough that either such a title is repeated or that the same title is used more than a hundred times anyway.

Also note that theoretically this plugin can be used without a source/title, if such behavior is desired. Just set the target field when creating the document and any source will be ignored.

Update: It's now also possible to set a max-length for aliases. Setting monguurl({ length: 40 }) will cut the alias approximately at the space (dash) closest before the limit. If there's no space/dash, the string will be cut off at the limit anyway. The final length might be up to 6 bytes longer to accomodate for appended numbers. The default length is 0, which is unlimited.